Larson Davis System 824, Техническое справочное руководство

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D-16 824 Reference Manual 9/29/09
Background: The all encompassing sound at a given location
caused by all sources of sound, but excluding the source to
be measured. It is essentially the sound that interferes with a
measurement.
Pink: It is a random sound that maintains constant energy
per octave. Pink light is similar to pink noise in that it has a
higher level at the lower frequencies (red end of the
spectrum).
White: It is a random sound that contains equal energy at
each frequency. In this respect, it is similar to white light.
Noise Dose (D)
It is the percentage of time a person is exposed to noise that
is potentially damaging to hearing. Zero represents no
exposure and 100 or more represents complete exposure. It
is calculated by dividing the actual time of exposure by the
allowed time of exposure. The allowed time of exposure is
determined by the Criterion Duration and by the sound level
(the higher the level, the shorter the allowed time). The
sound levels must be measured with A-frequency weighting
and slow exponential time weighting. See Projected Noise
Dose.
where
T is Measurement Duration
T
c
is Criteria Time
L
i
is TWA
L
c
is Criteria Level
q is exchange rate factor; see page D-8 "Exchange Rate (Q),
Exchange Rate Factor (q), Exposure Factor (k)"
Standard : ANSI S12.19
D
100 T
T
c
------------10
L
i
L
c
–
( )
q
⁄
=